public <T extends @Nullable Object> T[] toArray(T[] array) {
      return standardToArray(array);
    }

    @Override
    public boolean contains(@CheckForNull Object o) {
      return Maps.containsEntryImpl(delegate(), o);
    }

    @Override
    public boolean containsAll(Collection<?> c) {
      return standardContainsAll(c);
    }

    @Override
    public boolean removeAll(Collection<?> c) {

        return ObjectArrays.toArrayImpl(delegate(), array);
      }
    }

    @Override
    public boolean contains(@CheckForNull Object o) {
      synchronized (mutex) {
        return Maps.containsEntryImpl(delegate(), o);
      }
    }

    @Override
    public boolean containsAll(Collection<?> c) {
      synchronized (mutex) {
        return Collections2.containsAllImpl(delegate(), c);
      }

        return ObjectArrays.toArrayImpl(delegate(), array);
      }
    }

    @Override
    public boolean contains(@CheckForNull Object o) {
      synchronized (mutex) {
        return Maps.containsEntryImpl(delegate(), o);
      }
    }

    @Override
    public boolean containsAll(Collection<?> c) {
      synchronized (mutex) {
        return Collections2.containsAllImpl(delegate(), c);
      }

   * @param o the object that might be contained in {@code c}
   * @return {@code true} if {@code c} contains {@code o}
   */
  static <K extends @Nullable Object, V extends @Nullable Object> boolean containsEntryImpl(
      Collection<Entry<K, V>> c, @CheckForNull Object o) {
    if (!(o instanceof Entry)) {
      return false;
    }
    return c.contains(unmodifiableEntry((Entry<?, ?>) o));
  }

  /**

   * @param o the object that might be contained in {@code c}
   * @return {@code true} if {@code c} contains {@code o}
   */
  static <K extends @Nullable Object, V extends @Nullable Object> boolean containsEntryImpl(
      Collection<Entry<K, V>> c, @CheckForNull Object o) {
    if (!(o instanceof Entry)) {
      return false;
    }
    return c.contains(unmodifiableEntry((Entry<?, ?>) o));
  }

  /**